1. Field of the Invention
This invention relates to a general synthetic method for making organic non-linear optical materials which are useful in various applications such as in the fabrication of electro-optic devices.
2. Description of the Related Art
Electro-optic materials contain highly polarizable electrons. When an electric field is applied to these materials, the electron polarization changes significantly, resulting in an increase in index of refraction and a decrease in the velocity of the light passing through the materials. This electric field-dependent index of refraction change can be configured to perform a variety of functions such as transduction of electrical signals to optical signals, optical switching, millimeter wave signal generation, optical beam steering, radio-frequency detection, microwave-frequency detection, millimeter wave-frequency detection, phase control, power splitting, and wavelength division multiplexing (WDM). Devices that utilize electro-optic materials can be used in a wide variety of applications, e.g., signal transduction for cable television (CATV), broadband internet access, full scale holographic projection, gyroscopes for missile guidance, etc.
A number of inorganic and organic electro-optic materials are known. Organic electro-optic materials typically contain an organic non-linear optical chromophore that is dispersed or attached to a polymeric matrix. The chemical structures of some typical organic non-linear optical chromophores are shown in FIG. 1. As illustrated in FIG. 2, organic non-linear optical chromophores generally have one or more electron-withdrawing groups at one end and one or more electron-donating groups at the other, linked together by extended conjugation. The conventional synthetic strategy for preparing organic non-linear optical chromophores has been to build the chromophore from the electron-donating end, step by step, toward the electron-withdrawing end as illustrated in FIGS. 3A and 3B. Although hundreds of organic non-linear optical chromophores have been prepared using the conventional synthetic strategy, in many cases the syntheses have numerous steps, in some cases leading to lower yields and higher overall costs. Hence, the conventional synthetic strategy for preparing organic non-linear optical chromophores is not entirely satisfactory.